1. Field of the Invention
This invention relates to a pneumatic tire, and is concerned with restraint of uneven wear of a pneumatic tire, in particular restraint of uneven wear of a pneumatic tire of a block pattern provided with blocks having acute angle corners.
2. Description of the Prior Art
Because of problems in relation to steering stability, appearance, drainage and noise, lateral grooves in block-type tread patterns adopted on normal passenger tires are mostly arranged not to be parallel with the axial direction of the tire and the blocks are shaped as parallelograms. Further many ordinary or all-weather tires are provided with sipes (or fine grooves) substantially parallel with the axis of the tire to obtain steering stability on a wet road. However, such sipes made rigidity distribution of the blocks unbalanced, so that the blocks were distorted in the ground contact area and uneven wear was produced.
On the other hand, in the case where the sipes (or fine grooves) are arranged parallel with the lateral grooves, the rigidity of the blocks as a whole was lowered and steering stability was degraded. Therefore, means such as making the lateral grooves or sipes shallow was used. However, the above mentioned shallowing of the grooves or the sipes caused poor drainage and bad appearance at the terminal stage of use of the tire.
An object of the present invention is to overcome the above mentioned disadvantages of the prior art, and provide a pneumatic tire which restrains uneven wear without degrading drainage and appearance at the terminal stage of use of the tire.